Flow control valve for fluid motors and the like



Nov. 15, 1966 G. J. MARTIN 3,285,282

FLOW CONTROL VALVE FOR FLUID MOTORS AND THE LIKE I Filed Oct. 22, 1964TANK 28 p INVENTOR GEORGE J. MART/IV BY iwflzw f 100M ATTORNEYS UnitedStates Patent 3,285,282 FLOW CONTROL VALVE FOR FLUID MOTORS AND THE LIKEGeorge J. Martin, Lyndhurst, Ohio, assignor to Parker- HannifinCorporation, Cleveland, Ohio, a corporation of Ohio Filed Oct. 22, 1964,Ser. No. 405,675

11 Claims. (Cl. 137--596) The present invention relates generally asindicated to a. flow control valve for fluid motors and the like andmore particularly to a flow control valve which is pressure sensitive,i.e., when the fluid pressure increases, the rate of flow of fluidthrough the flow control valve decreases.

In the case of a fork lift truck, for example, it is conventionalpractice to employ a single acting hydraulic motor which, when fluidunder pressure is conducted thereto, is operative to raise the liftingfork and a load thereon and which, when the fluid therefrom is permittedto drain into a tank, the lifting fork and load thereon descends. Ifsuch lifting fork has a heavy load thereon and is allowed to descend attoo rapid a rate, the lift truck will be subject to severe shock loadand, in fact, may be tipped when the lifting fork and load is suddenlystopped during descent or at the end of the stroke.

Accordingly, it is a principal object of this invention to provide aflow control valve which is sensitive to fluid pressure to permit rapiddescent of a piston in a cylinder under light load and to permitprogressively decreased rate of descent of the piston as the load isprogressively increased. Thus, in the case of a fork lift truck, forexample, the lift fork when empty, or lightly loaded, will descend at arapid rate, as desired, when the directional control valve is operatedto permit such descent. On the other hand, when the lift fork has aheavy load thereon, and the directional control valve is operated topermit lowering thereof, the present flow control valve willautomatically restrict the flow according to the magnitude of the load.

Other objects and advantages of the present invention will becomeapparent as the following description proceeds. To the accomplishment ofthe foregoing and related ends, the invention, then, comprises thefeatures hereinafter fully described and particularly pointed out in theclaims, the following description and the annexed drawing setting forthin detail a certain illustrative embodiment of the invention, this beingindicative, however, of but one of the various ways in which theprinciple of the invention may be employed.

In said annexed drawing:

FIG. 1 is a side elevation view partly in cross-section illustrating atypical fork lift truck employing a single acting fluid motor forraising and lowering the lifting fork thereof; a

FIG. 2 is a cross-section view through a flow control valve embodyingthe present invention, said flow control valve being shown inassociation with a directional control valve for a single actingcylinder, said directional control valve being here shown by way ofexample as a three way spool-type valve; and

FIG. 3 is a fragmentary cross-section view of a moditied form of flowcontrol valve.

Referring now in detail to the drawing; and first to FIG. 1, thereference numeral 1 denotes a fork lift truck to the lower front portionof which a telescoping mast structure 2-3 is pivotally mounted at 4.Said mast structure 2-3 is adapted to be tilted back about pivot 4 as bya double acting fluid motor 5 pivotally connected to the ice maststructure at 6 and pivotally connected at its other end (not shown) tothe truck frame.

As aforesaid, the mast structure 2-3 herein is of telescoped formincluding a lower section 3 in which the upper section 2 is verticallyslidably guided and, in turn, the lifting fork 7 is vertically slidablyguided in said upper section 2. Mounted on the pivot 4 is thesingle-acting cylinder 8 having its piston rod 9 linked by chains or thelike, not shown, to cause vertical movement of the upper mast section 2with respect to the lower mast section 3 and upward movement of thelifting fork 7 with respect to the upper m-a'st section 2. When thepiston 10 (see FIG. 2) moves down in the cylinder 8, the upper section 2moves down into telescoped relation within the lower section 3 of themast structure and then the lifting fork 7 moves down with respect toboth sections 2 and 3 for placing the load W on the floor F. This isschematically shown in FIG. 2 wherein the load W is lifted by admittingfluid under pressure from pump 11 via the directional control valve 12into the lower end of the cylinder 8, and the load W is permitted todescend when the fluid in the cylinder 8 is allowed to escape into thereservoir or tank 14, via the directional control valve 12.

Referring now in detail to FIG. 2, there is provided a housing 15 whichhas a bore 16 therethrough intersected by a bypass passage 17 which atone end communicates with the inlet port 18 and which at the other endcommunicates with tank port 19, by a pair of pressure feed passages 20,20 which straddle the branches 2-1, 21 of the bypass passage, by a pairof motor passages 23, 23, and by a pair of return passages 24, 24 whichlead to the aforesaid tank port 19.

Reoiprocable in said bore 16 is a three-way valve spool 25 and it can beseen that when said spool 25 is in the neutral position N as shown inFIG. 2, the pump 11 will freely circulate fluid through the bypasspassage 2117 into the tank 14. When the spool 25 is shifted to raiseposition R, the bypass passage 21-17 will be closed by the lands 26 and27, and fluid communication will be opened between the right pressurefeed and motor passages 20 and 23, whereby fluid under pressuredelivered by the pump 11 into the inlet port 18 Will flow through thecheck valve 28 into the right pressure feed passage 20 and thence to theright motor passage 23 wherefrom the fluid under pressure flows throughthe passages 29 and 3 0 and through the flow control valve 31 into thelower end of the cylinder 8 thus to act on the piston 10 to raise thesame and the load W thereon.

When the spool 25 is shifted to the lower position L, the bypass passage21-17 remains open, and fluid communication is established between theright motor passage 23 and the right return passage 24, whereby the loadW on the piston 10 will displace the liquid in the cylinder 8 throughthe flow control valve 31 and passages 30 and 29 into the tank 14 viathe right motor and return passages 23 and 24 and tank .port 19. Whenthe spool is in neutral position N, the lands 27 and 32 thereof blockcommunication of the right motor passage 23 with the adjacent pressurefeed and return passages 20 and 24, whereby fluid is trapped in thecylinder 8 so that the piston 10 and load W thereon are locked in raisedposition.

In FIG. 1, the operating lever 34 will be operatively connected with thespool 25 to shift it to its various positions aforesaid and it isunderstood that the valve housing 15 may have another spool therein forcontrolling the mast tilt cylinder 5. Furthermore, while not shownherein, the spool 25 may have associated therewith the usual springcentering mechanism which automatically returns the spool to the Nposition upon release of the control lever 34, and it is furthercontemplated that suitable detent mechanisms may be employed toyieldably retain the spool 25 in either or both the R and L positions,whereby the operator may manipulate the lever 34 to the desired positionand use both hands for driving the truck while the load W is beingraised or lowered.

The flow control valve 31 herein comprises a sleeve member 40 havingpassages 41 through the wall thereof which register with the annularpassage 42 in the housing 15. Reciprocable in said sleeve member 40 isthe flow control member 43 which has a plurality of apertures 45 ofvarying sizes therethrough which, as can be seen, when the flow controlmember 43' moves to the right as viewed in FIG. 2, the largest apertures45 will progressively be covered by the right edges of the passages 41of the sleeve member 40 to decrease the aggregate flow capacity throughapertures 45. As the member 43 continues to move to the right the secondlargest, then the third largest, etc., apertures 45 will progressivelybe covered until only the smallest apertures 45 will remain uncoveredfor most restricted flow. The member 43 is capable of movement to theright even to the extent where the smallest apertures 45 are covered bythe right edges of the sleeve passages 41, whereby exhaust flow from thecylinder 8 under extremely heavy load may be substantially completelyblocked except for leakage around the sleeve member 40 and through thesliding fit between the flow control member 43 and sleeve 40.

The flow control member 43 is biased to its full open position, as shownin FIG. 2, by the spring 46 which bears on the member 47, and saidplunger member 47, in turn, bears on flow control member 43 throughspring 48 and plug member 49. Said plunger member 47 has a plunger stem50 which is axially slidably sealed in cylinder member 51. The plug andplunger members 49 and 47 have pressure equalizing orifices 52 and 53therethrough so that the fluid pressures in the chambers 54 and 55 willbe equal to that in the chamber 56 in the flow control member 43. Thehousing has a passage 57 leading from passage 30 to chamber 58 so thatfluid pressure may act on the end of plunger stem 50.

When the spool 25 is in the neutral position N, the flow control member43 will be in the position shown in FIG. 2 regardless of the load W onthe piston 10, since in that condition of the spool 25, the pressuresare equalized on both sides of the plunger stem 50 in the chambers 56,54 and 55 and in the passages 30 and 57 and chamber 58. However. whenthe spool 25 is shifted to the lower position L, the communication ofthe motor passage 23 with the right return passage 24 results in apressure drop in the passages 29, 30 and 57 and in chamber 58 leading tothe plunger stem 50, whereupon the higher pressure in the chambers 56,54, and 55 acting on the area of said plunger stem 50 will cause theflow control member 43 to move to the right compressing spring 46 thusto decrease the flow rate through the apertures 45. The greater the loadW, the greater the pressure differential acting on plunger stem 50 dueto decreasing flow capacity through apertures 45 and thus as the load Wis increased, the rate of descent thereof is decreased.

When the load W on the piston 10 is a minimum, that is, the weight ofthe lifting fork 7 and of the upper mast section 2, the bias of thespring 46 is preferably such that the plunger stem 50 will not movetoward the right under the influence of the relatively small fluidpressure diiferential in the chambers 56 and 58.

Assuming now that the lifting fork 7 has a maximum load W thereon forwhich the equipment is designed, such that, for example, there is builtup a pressure of 1000 psi. on the liquid in the lower end of thecylinder 8. So long as the spool 25 is in its neutral position N such1000 psi. pressure is prevalent throughout the system from cylinder 8 tomotor passage 23, and thus all of the parts of the flow control assemblywill remain as shown in FIG. 2. However, when the spool 25 is shifted tolower position L, the pressure in the chamber 58 will drop substantiallywhereupon the pressure in the chambers 56, 54, and 55 acting on the areaof the plunger stem 50 will compress the spring 46 to permit movement offlow control member 43 to the right to decrease the flow capacitythrough the apertures 45 to the desired extent so that the lifting fork7 and its load W will descend at the desired rate so as not to shock theequipment or to tip it over when the fork 7 reaches its lowest point, orwhen the spool 25 is shifted back to neutral position N. Similarly, whenthe fork 7 has a load W thereon between minimum and maximum, theresulting pressure differential in the chambers 56 and 58 will compressthe spring 46 to less extent with the result that the flow controlmember 43 will move to the right to permit flow through apertures 45 ata desired rate which will be less than the maximum rate (with no load onfork 7) but greater than the minimum rate (with maximum load W on fork7).

When the spool 25 is shifted to raise position R, the motor passage 23is communicated with the feed passage 20 whereupon fluid under pressureflows through passages 29 and 30, and apertures 45 to the lower end ofcylinder 8 to raise the load W. In that case, the pressure in chamber 58is greater than in chambers 56, 54, and 55 due to pressure drop inpassage 30 and apertures 45 and thus the flow control member 43 will beheld in FIG. 2 position by spring 46 and by the higher fluid pressure inchamber 58 acting on the end of the plunger stem 50. The pressure dropacross passage 59 also aids in maintaining flow control member 43 in itsmaximum flow position.

With further reference to the flow control member 43, and plunger member47, they are, in effect, integral, but because of the provision of theequalizing orifice 52 of smaller size than the equalizing orifice 53,the chamber 54 becomes a dashpot or cushioning chamber to minimize theefiect of shock loads in the system. For example, when the spool 25 isshifted from lower position L to neutral position N the load W will besuddenly stopped and its 7 inertia will cause shock pressure in thesystem, but because of the orifice 52 the pressure in the chamber 54cannot be instantly increased and thus plug member 49 may move slightlyto the right compressing spring 48 to isolate the shock from plungermember 47. Moreover, if the load W is a very heavy one, only thesmallest apertures 45 will be open to dissipate shock pressures in thedownstream passages 30, 29, and 57.

'When the load W is at rest with the spool 25 in the neutral position N,pressure in the system due to the load W will be equalized and the flowcontrol elements, that is, the flow control member 43, the plug member49, the plunger member 47 and the cylinder member 51 will be in thepositions shown in FIG. 2. Now, if the spool 25 is shifted to raiseposition R, the pressure in the system will have to increase to a valuegreater than that due to the load W in order to overcome the inertia ofthe load W and to raise the load. As the pressure supplied by the pump11 flows into the system through the inlet port 18, check valve 28,pressure feed passage 20, and motor passage 23, the increasing fluidpressure may tend to actuate the cylinder member 51 toward the leftagainst the spring 46 to displace the fluid in the chamber 55 throughthe equalizing orifice 53 into the chamber 54 and the build-up ofpressure in the chamber 54 (due to smaller orifice 52) resists theopposing pressure in chamber 56 so as to avoid pulsating or flutteringmovement of the flow control member 43. Here again the chamber 54 (andalso chamber 55) acts as a cushioning chamber or dashpot.

In the modification illustrated in FIG. 3, the chamber 58 is vented tothe atmosphere by passage 60 instead of being communicated with passages29 and 30 by way of passage 57 as in FIG. 2. Accordingly, static fluidpressure in chambers 56, 54, and 55 will move plunger stem 50 to theright against spring 46 a distance proportional to the magnitude of thepressure, thus correspondingly relaxing the spring 48. When the spool 25is shifted to lower position L with a heavy load W on piston 10 even avery small pressure drop across passage 59 will move the members 43 and49 against relaxed spring 48 to effect substantial restriction of flowby apertures 45. On the other hand if there is a light load W, thespring 46 will not be further compressed at all or only very slightlywhereby even a substantial pressure drop across passage 59 will not movethe member 43 appreciably against spring 48 to flow restricting positionand thus the light load W can descend rapidly. In this FIG. 3embodiment, the spring 46 is sufficiently strong so as not to requireassistance of fluid pressure in chamber 58 as is the case in FIG. 2wherein fluid pressure has access to chamber 58 through passage 57.Accordingly, when spool 25 is shifted to raise position R, the pressuredrop across passage 59 and the force of spring 48 will urge the sleeve43 toward the left for full flow through apertures 45 even though highpressure due to heavy load W holds the plunger 47 at its rightwardactuated position.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of the following claims, or the equivalent ofsuch, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A flow control valve'comprising a housing having a passagetherethrough, a flow control sleeve means having an aperture through thewall thereof disposed in said housing for movement in one direction froma position whereat said aperture is in direct open alignment with saidpassage to effect a progressive closing of said aperture as saidaperture is moved out of alignment with said passage, means within saidhousing defining a chamber having restricted fluid communication withfluid pressure upstream of said aperture, a fluid pressure actuatedplunger in said housing having its respective ends exposed to fluidpressure downstream of said aperture via a branch passage leading to oneend of said plunger and to fluid pressure in said chamber, and springmeans biasing said plunger and sleeve means in a direction maintainingsaid aperture in such direct open alignment with said passage, saidchamber constituting a cushioning chamber to resist sudden changes influid pressure therein.

2. A flow control valve comprising a housing having a passagetherethrough, and a flow control member movable in said housing to varythe rate of flow of fluid through said passage, said flow control membercomprising a plunger means having a portion thereof exposed to fluidpressure on the upstream side thereof for actuation thereby, sleevemeans axially reciprocable in a bore in said housing and havingapertures through the wall thereof, first spring means biasing saidplunger means in opposition to such fluid pressure for yieldablymaintaining said sleeve means in a position whereat said apertures arein full fluid communication with said passage, said sleeve means alsohaving a portion thereof exposed to fluid pressure on the upstream sidethereof for actuation thereby in one direction during actuation of saidplunger means by increasing fluid pressure to cause a progressiveclosing of said apertures for reduced fluid communication between saidapertures and passage, and a second spring means between said plungermeans and sleeve means for exerting decreasing resistance to movement ofsaid sleeve means in such one direction as said plunger means is thusactuated by increasing fluid pressure.

3. The valve of claim 2 wherein said plunger means has another portionopposite said first mentioned portion vented to the atmosphere.

4. The valve of claim 2 wherein said plunger means has another portionopposite said first mentioned portion exposed to fluid pressuredownstream of said apertures via a branch passage leading to one end ofsaid plunger means.

5. The valve assembly of claim 2 further comprising a plug memberdisposed in said bore between said sleeve means and plunger means, saidplug member being maintained in engagement with said sleeve means bysaid sec- 0nd spring means and defining with said plunger means and thewall of said bore a chamber having restricted fluid communication withthe fluid pressure on the upstream side thereof to minimize the effectof shock loads on said plunger means.

6. A flow control valve comprising a housing having a passagetherethrough, a flow control sleeve axially slidably received in a borein said housing and having apertures through the wall thereof, a plungerand plug member disposed in said bore with said plug member locatedbetween said sleeve and plunger, said plug member and plunger definingwith the wall of said bore a first chamber having restricted fluidcommunication with fluid pressure upstream of said apertures, springmeans engaging said plunger for biasing said plunger and thus saidsleeve in a direction maintaining said apertures in substantially fullfluid communication with said passage, said plunger also defining withthe wall of said bore a second chamber having restricted fluidcommunication with said first chamber, said plunger having a stemportion projecting into said second chamber, and means for isolating theouter end of said stern portion from the fluid pressure in said secondchamber so as to provide a larger area on said plunger exposed to fluidpressure in said first chamber than in said second chamber, wherebythere is a progressive movement of said plunger and thus said sleeve inthe opposite direction for effecting a progressive reduction in fluidcommunication between said passage and apertures as the fluid pressureupstream of said apertures is increased.

7. The valve of claim 6 wherein said outer end of said stem portion isexposed to the atmosphere.

8. The valve of claim 6 wherein said outer end of said stem portion isexposed to fluid pressure downstream of said apertures via a branchpassage leading to said outer end of said stem portion.

9. The valve of claim 8 wherein said means for isolating the outer endof said stem portion from the fluid pressure in said second chambercomprises a cylinder member disposed in said bore for receipt of saidstem portion, and there is a greater fluid restriction between saidfirst chamber and the fluid pressure upstream of said apertures thanbetween said first and second chambers, whereby any increase in thefluid pressure in said second chamber will be resisted by the opposingpressure in said first chamber so as to avoid fluttering of said flowcontrol sleeve.

10. A valve assembly for actuation of a fluid motor comprising a housinghaving an inlet port for connection with a fluid pressure source, amotor port for connection with a fluid motor, and a return port forconnection with a fluid reservoir; a directional control valve membermovable in said housing from a neutral position blocking fluidcommunication between said motor port and said inlet and return ports tooperating positions selectively communicating said motor port with saidinlet port or said return port; and a flow control valve containedwithin said housing for varying the rate of flow of fluid from saidmotor port to said return port when said valve member is in thatoperating position, said flow control valve comprising a plunger meanshaving a portion thereof exposed to fluid pressure on the motor portside thereof for actuation thereby, a sleeve means axially reciprocablein a bore in said housing and having apertures through the wall thereof,first spring means biasing said plunger means in opposition to suchmotor port fluid pressure for yieldably maintaining said sleeve means ina position whereat said apertures are in full fluid communication withsaid motor port, said sleeve means also having a portion thereof exposedto fluid pressure on the motor port side thereof and actuated thereby inone direction during actuation of said plunger means by increasing fluidpressure in said motor port to cause a progressive closing of saidapertures for reduced fluid communication between said apertures andmotor port, and a second spring means between said plunger means andsleeve means for exerting decreasing resistance to movement of saidsleeve means in such one direction by flow of fluid therethrough as saidplunger means is thus actuated by increasing fluid pressure.

11. The valve assembly of claim 10 further comprising a plug memberdisposed in said bore between said sleeve means and plunger means, saidplug member being maintained in engagement with said sleeve means bysaid second spring means and defining with said plunger means and thewall of said bore a chamber having restricted fluid communication withfluid pressure in said 10 motor port to minimize the effect of shockloads on said plunger means.

References Cited by the Examiner UNITED STATES PATENTS M. CARY NELSON,Primary Examiner.

MARTIN P. SCHWADRON, Examiner.

R. J. MILLER, Assistant Examiner.

1. A FLOW CONTROL VALVE COMPRISING A HOUSING HAVING A PASSAGETHERETHROUGH, A FLOW CONTROL SLEEVE MEANS HAVING AN APERTURE THROUGH THEWALL THEREOF DISPOSED IN SAID HOUSING FOR MOVEMENT IN ONE DIRECTION FROMA POSITION WHEREAT SAID APERTURE IS IN DIRECT OPEN ALIGNMENT WITH SAIDPASSAGE TO EFFECT A PROGRESSIVE CLOSING OF SAID APERTURE AS SAIDAPERTURE IS MOVED OUT OF ALIGNMENT WITH SAID PASSAGE, MEANS WITHIN SAIDHOUSING DEFINING A CHAMBER HAVING RESTRICTED FLUID COMMUNICATION WITHFLUID PRESSURE UPSTREAM OF SAID APERTURE, A FLUID PRESSURE ACTUATEDPLUNGER IN SAID HOUSING HAVING ITS RESPECTIVE ENDS EXPOSED TO FLUIDPRESSURE DOWNSTREAM OF SAID APERTURE VIA A BRANCH PASSAGE LEADING TO ONEEND OF SAID PLUNGER SAID FLUID PRESSURE IN SAID CHAMBER, AND SPRINGMEANS BIASING SAID PLUNGER AND SLEEVE MEANS IN A DIRECTION MAINTAININGSAID APERTURE IN SUCH DIRECT OPEN ALIGNMENT WITH SAID PASSAGE, SAIDCHAMBER CONSTITUTING A CUSHIONING CHAMBER TO RESIST SUDDEN CHANGES INFLUID PRESSURE THEREIN.